Related Art
A number of processes have been proposed to recover lithium from lithium-containing minerals. For example, in U.S. Pat. No. 2,974,884 Martin and Lanbolt disclose a process wherein lithium is recovered from spodumene and minerals consisting of lithia, silica and alumina. "Spodumene" refers to a white to yellowish-purplish- or emerald-green clinopyroxene igneous mineral occurring in prismatic crystals, and may also be known as triphane. It has a general formula of LiAlSi.sub.2 O.sub.6, a hardness of 6.5 to 7 (on Moh's scale), and a specific gravity of 3.13-3.20. Usually, the ore contains about 0.1-4 percent by weight of Li.sub.2 O. This patent is concerned with recovery of lithium from a finely ground concentrated spodumene ore by use of sulfuric acid in a closed container under high pressure and high temperature, namely over 50 psig and 250.degree. to 450.degree. C. The concentrated spodumene is obtained by grinding the ore material to about 60 mesh, flotation treating (such as with 1/2 to 5 pounds of a higher fatty acid derived from tall oil and 1/2 to 3 pounds of methyl isobutyl carbinol flotation agent, per ton of ore) to provide a slime, concentrate and a tails component. The concentrate and slime are then reground to produce a mix for the high pressure sulfuric acid recovery. The ground ore may be treated with an aqueous cleansing or conditioning solution, such as an aqueous solution of sodium hydroxide, at a rate of 1-8 pounds per ton of ore. This process is disadvantageous in requiring many steps, including a flotation process, as well as high temperatures and pressures.
In U.S. Pat. No. 3,007,770, Kawecki and Cole disclose the extraction of lithium from a spodumene ore involving heating the spodumene in the crushed state to a temperature of at least about 1000.degree. up to 1300.degree. C. The product is then treated with hydroxide or carbonate of sodium or potassium. The resulting slurry is treated with dilute sulfuric acid to a pH value not lower than 4.2, followed by treatment with hydrogen peroxide. This procedure is also disadvantageous in that it requires heating to over 1000.degree. C. to render the spudomene ore amenable to further chemical reaction.
In U.S. Pat. No 3,189,407, Betton et al. disclose the separation of lithium from lepidolite ore and similar complex minerals. The process involves, first, reaction of the mineral with 65-75 percent by weight aqueous sulfuric acid at about 140.degree. to 200.degree. C. The slurry obtained is filtered, and the lithium is recovered by treatment with carbonate as the lithium carbonate. Again, this process requires high slurry temperatures which are expensive, both as to heat and acid consumption.
In this application, a lithium-bearing trioctahedral smectite, a member of the montmorillonite group of clay minerals, is the source of lithium. A major deposit of hectoritic montmorillonite clay is the McDermitt Caldera complex on the Nevada-Oregon border, which because of its size contains a significant percentage of the world's supply of lithium. The clay is a complex and variable solution and/or intimate physical mixture of solid montmorillonite clay component end members of which hectorite is typically a major constituent. Glanzman and Rytuba discuss the McDermitt Caldera geology in "Zeolite Clay Mineral Zonation of Volcaniclastic Sediments Within the McDermitt Caldera Complex of Nevada and Oregon", U.S. Geological Survey Open-File Report No. 79-1668 (1980) and detail the mineral zonation of the McDermitt Caldera complex. Previous attempts to extract the lithium from these clays by hydrometallurgical procedures have been unsuccessful.
For instance, Starkey, et al. in Journal Research U.S. Geol. Survey, Vol. 5, No. 2, March-April, pp. 235-242 (1977) disclose the treatment of a hectorite-like ore with acids and with 2.5N sodium hydroxide. The sodium hydroxide treatment is indicated to have no more effect on the release of lithium from hectorite-like ore than distilled water, sea water, or sodium chloride solution.
May et al., in "Extracting Lithium from Clays by Roast Leach Treatment", ROI 8432, U.S. Bureau of Mines Report (1980) disclose an investigation of the extraction of lithium from clay from the northern and southwestern sections of the McDermitt Caldera. Lithium extractions using sulfuric acid were obtained ranging from 60-90% from the clay from the northern part (McDermitt A sample). In contrast, the clay from the southwestern part (McDermitt B sample) was much more resistant to extraction using dilute sulfuric, and no more than 1% of the lithium was removed. In two experiments, McDermitt B hectoritic montmorillonite clay at a 10% solids level was treated with sulfuric acid of pH of 1 for three hr, probably at ambient temperature. In the first experiment, 226 pounds of H.sub.2 SO.sub.4 was required per ton of clay and the lithium extraction is 0.7 percent. In the second experiment 451 pounds of sulfuric acid were added per ton of clay and a 1.1 percent of lithium extraction was obtained. Higher lithium extractions were obtained using very large amounts of sulfuric acid and/or using extremely high temperature roasting treatments (of the order of 500.degree. to 1000.degree. C.). However, none of the approaches described by May et al. appear to be economically feasible to recover the lithium in useful form.
The recovery of lithium from various sources is also reviewed in "Lithium and Lithium Compounds" by R. Bach, pp 448-476 in Kirk-Othmer: Encyclopedia of Chemical Technology, 3rd Ed, Vol 14, published in 1980 by John Wiley and Sons, Inc. of New York, N.Y. None of the references described above disclose methods comparable in effectiveness of the present invention to extract lithium from low grade lithium ores.
This invention provides a new process of general applicability for obtaining lithium from material having a low concentration of lithium, (e.g., recycle operations from spent batteries) and particularly lithium-containing ores and clays (smectite, montmorillonite or hectorite), whereby lithium can be recovered without the use of high temperatures and pressures and at relatively low cost. Further, this process provides an alternative method for obtaining lithium carbonate from richer lithium ores for a variety of subsequent uses.